Just weigh the bottle or give it shake to feel liquid level! You should see frosting of bottle indicating liquid level when used !
I think this may be an internet fact. My 4.5 kg gas thing says 13 06, there's a drop of gas left in it, so I weighed it Six kilos dead - that's 13.2 lbs so as near as damn it - 13lbs 3 ounces. Which is less than the apparent weight of the empty container - makes no sense?
You can find the specs on the website https://www.calor.co.uk/shop/gas-bottles/4-5kg-butane-gas-bottle.html
I have a laser guided thermometer with a red dot style laser on it. It reads temperatures in centigrade or olde English. It’s exceptionally accurate from about a foot up to about ten feet, slightly less accurate the further away you get, perhaps a half a degree or so out. Very very useful for finding your gas levels and loads of other stuff too. Keep one in your garage and you’ll know exactly how much you use on a regular basis and more importantly, when you are getting low. My pal puts a magic marker line on exactly where his level is when he’s unpacking after an expedition, sometimes he double checks before he packs for the next adventure. Ozziedog,,,,,,,,,,,, £25 ish plus postage